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Aero Peru 603

Accident Case Study

The conventional wisdom on this mishap is rather maddening:

  • The static ports were covered with metallic duct tape prior to washing, the technician forgot to remove the tape, the inspector didn't see that.
  • The captain, who performed the external preflight, failed to see the tape. The static ports are 15 feet off the ground and it was at night, they say, so this is "understandable."
  • The pilots were barraged with incorrect information throughout the flight. They had airspeed indicators that told them they were too fast, they had altimeters that were not working but later seemed to agree with ATC, they had ground proximity warning alerts. They faced an "impossible task" of figuring out what was right and what was wrong.

The accident report blames the technician for not removing the tape and the pilots for failing to comply with the GPWS procedure. I believe the pilots could have done much more prior to the GPWS warning. The mishap was survivable and easily so.

  • The pitot-static ports are so vitally important, they must be inspected carefully on every external preflight, even if that means getting a ladder.
  • During takeoff the first issue they faced was an altimeter that didn't move and airspeed indications that didn't make sense. Their attitude indicator worked perfectly. All they had to do was keep the aircraft in a known pitch for the known power.
  • They asked ATC for an indication of their speed, which was very smart. The radar indications can be tracked and converted to speed. That reassured them.
  • A few minutes later their altitude went from zero to 9,700 feet so they were overjoyed that it was working again. They asked ATC for their altitude indication and were told it was indeed 9,700 feet. Of course ATC's altitude indication comes from the aircraft transponder so it would have to agree.
  • Their airspeed indicators showed they were gaining speed so they pulled the throttles to idle. They got overspeed warnings and other indications they were flying too fast. The Captain, at several points, said "My engines are at idle, we are maintaining altitude, and yet we are still accelerating." That should have been a clue, but it wasn't. He pulled the speed brakes.
  • As the airplane descended with the throttles at idle and the speed brakes pulled they got GPWS warnings. They asked ATC again for their altitude and were reassured it was still 9,700 feet but their speed had declined. Now the pilots were really confused. They impacted the ocean and all aboard were killed.
  • Yes, it is easy to second-guess after the fact. But a little systems knowledge should have told them the GPWS was using the radio altimeter which had no indication of failure. The ATC altitude read out was from their aircraft's static system which was already suspect. They had lots of fuel, an attitude indicator that would help them keep things level until they sorted it all out.
  • We practice this routinely in the simulator and have for as long as I've been flying. The warning horns and lights can be distracting, but you need to keep a calm, dispassionate view of the world when things go wrong.

 

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Photo: AeroPeru 603 Captain's Static Port, taken by underwater camera, from May Day: Flying Blind.

Accident Report

  • Date: 02 OCT 1996
  • Time: 01:16
  • Type: Boeing 757-23A
  • Operator: AeroPeru
  • Registration: N52AW
  • Fatalities: 9 of 9 crew, 61 of 61 passengers
  • Aircraft Fate:Destroyed
  • Phase: En route
  • Airport: (Departure) Lima-Jorge Chavez International Airport (LIM/SPIM), Peru
  • Airport: (Destination) Santiago-Arturo Merino Benitez Airport (SCL/SCEL), Chile

Narrative

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Figure: Flight Track, from Peru Ministry of Transport, Aircraft Accident Report, pg. 19.

[Peru Ministry of Transport Aircraft Accident Report, §1.]

  • At 05:42 UTC on 2 October 1996 the BOEING 757 AIRCRAFT WITH REGISTRATION N52AW, operated by the airline AEROPERÚ, took off from Jorge Chávez International Airport in Lima, Peru, to perform scheduled flight 603 to Santiago de Chile, with the following crew on board.
  • When they took off and reached speed V2 + 10, the crew noticed that the altimeters were not responding and that something irregular was occurring. They therefore decided to notify the control tower in Lima to declare an emergency, consulted Lima for confirmation of their altitude by radar, and requested assistance to return via radar vectors. After 29 minutes of flight, while returning to Lima airport and with the crew attempting to control the aircraft, it impacted with the sea 48 nautical miles from the airport, with the total loss of the aircraft and all of its occupants – 9 crew members and 61 passengers (70 people on board).

Probable Cause

[Peru Ministry of Transport Aircraft Accident Report, §3.]

  • It can be deduced from the investigation carried out that the maintenance staff did not remove the protective adhesive tape from the static ports. This tape was not detected during the various phases of the aircraft's release to the line mechanic, its transfer to the passenger boarding apron and, lastly, the inspection by the crew responsible for the flight (the walk-around or pre-flight check), which was carried out by the pilot-in-command, [REDACTED], according to the mechanic responsible for the aircraft on the day of the accident.
  • The pilot-in-command, [REDACTED], made a personal error by not complying with the procedure for GPWS alarms and not noticing the readings of the radio altimeters in order to discard everything which he believed to be fictitious.
  • The co-pilot, [REDACTED], made a personal error by not being more insistent, assertive and convincing in alerting the pilot-in-command much more emphatically to the ground proximity alarms.

See Also:

References

May Day: Flying Blind, Cineflix, Episode 4, Season 1, 17 September 2003 (AeroPeru 603)

Peru Ministry of Transport, Aircraft Accident Report, Accident of the Boeing 757-200 Aircraft, Operated by Empressa de Transporte Aereo Del Peru, Off the coast of Lima, 2 October 1996

Revision: 20140525
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